Public history is a wide-ranging field that includes archivists, museum workers, consultants, and many other careers. In short, public history is anything that puts "history to work in the world"* by making history accessible to and engaging for a broader audience beyond academics.
Their guide, How To Choose and Thrive in a Graduate Public History Program, offers advice about all things graduate school, from exploring types of careers to choosing a grad program in public history - right down to questions to ask once you've been accepted. Read more at http://ncph.org/wp-content/uploads/The-Public-History-Navigator-2015-Web.pdf.
* New Professional and Graduate Student Committee, National Council on Public History. 2015 (rev. 2016). How To Choose and Thrive in a Graduate Public History Program.